American Airlines has followed Southwest Airlines in paying to settle a case accusing US airlines of colluding to artificially boost airfare prices.

Bloomberg reports that the airline agreed to pay $45 million without admitting wrongdoing in the case.

The lawsuit, brought on the behalf of air travellers, alleges that American, Southwest, United, and Delta cooperated to drive airfares up during a period where demand for air travel was stagnant and operating costs like fuel were declining.

Southwest previously paid $15 million to settle its portion of the lawsuit.

The airlines were accused of agreeing to manipulate capacity to increase prices as well as working together to limit consumer access to ticket pricing information and bar foreign competition.

American and Southwest officials said they settled the case to avoid litigation costs. United and Delta vowed to continue defending against the lawsuit, which a United spokesperson said was “without merit.”

“The assertion that our success is due to anything but the hard work of our people is offensive,” added Delta spokesman Morgan Durrant.